Description of Nocardioides jiangsuensis sp. nov., and Proposal for Reclassification of the Genus Marmoricola as Nocardioides

Abstract

A Gram-staining-positive, non-motile, aerobic, spherical actinobacterium, designated WL0053^T, was isolated from the coastal sediment of Nantong City, Jiangsu Province, China. The 16S rRNA gene sequence of strain WL0053^T exhibited the highest similarities to Nocardioides mesophilus MSL-22^T (98.0%), N. massiliensis GD12^T (97.8%), Marmoricola bigeumensis MSL-05^T (97.6%), and N. jensenii DSM 20641^T (97.3%). The polyphasic taxonomic approach was used for the identification of strain WL0053^T. This strain formed white, round, and smooth colonies and grew in the presence of 0-18% (w/v) NaCl (optimum, 0-4.0%), at pH 6.0-9.0 (optimum, pH 7.0) and at 20-37 °C (optimum, 28 °C). The main cellular fatty acids comprised of C_17:1 ω8c, C_18:1 ω9c, and iso-C_16:0. The genomic DNA G + C content was 71.9%. The predominant quinone was MK-8(H₄), and the major polar lipid consisted of phosphatidylcholine, glycolipid, phosphatidylethanolamine, and two unidentified phospholipids. Phylogenetic trees of 16S rRNA gene and bac120 gene set indicted that strain WL0053^T was closely related to the species N. iriomotensis and N. mesophilus, while these two species clustered in a separate clade together with M. caldifontis YIM 730233^T in the bac120 tree. Combined with the analysis of average nucleotide identity (ANI), average amino acid identity (AAI), and digital DNA-DNA hybridization (dDDH), it can be considered that the strain WL0053^T is a new member of the genus Nocardioides and is proposed to be named as Nocardioides jiangsuensis sp. nov.. The type strain is WL0053^T (=MCCC 1K05897^T=JCM 34671^T=GDMCC 4.192^T). Furthermore, based on the fact that the genera Nocardioides and Marmoricola both appeared polyphyletic with no significant difference on phenotypic and chemotaxonomic traits, we proposed to reclassify the genus Marmoricola as Nocardioides.